Download of DriveSlim 1.0.1 for Mac was on the developer's website when we last checked. We cannot confirm if there is a free download of this app available. We recommend checking the downloaded files with any free antivirus. DriveSlim for Mac lies within System Tools, more precisely File Managers. The actual developer of this software for Mac is Prosoft Engineering, Inc.
From the developer:
DriveSlim is an easy to use Mac OS X app that will allow you to recover hard drive space by identifying and allowing you to click-to-delete large, duplicate or unused files. It will detect and recommend files that can be deleted from or backed up off of your system to help free space on your hard drive.
You may want to check out more Mac applications, such as Drive Genius 3 or DriveGenius, which might be similar to DriveSlim.